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help the up_conversion mixer

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Member level 5
Oct 5, 2006
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when i design a quadrature up_conversion mixer

the out wave of (outp-outm) is just like this

who can tell me the reason?

you are plotting the freqs Fin+Flo and Flo-Fin.
for example:Fin=900MHz, Flo=1GHz, Fout=1.9GHz AND 100MHz.
Just add a filter at the output to filter out the unwanted freq.
I hope it can help

all the devices is ideal ,so there is no mismatch, to a quadrature mixer,

so? do you know what is the quadrature mixer??

i am sorry that if the LO is 4G , the IF is 20M,

so tell me how to add a filter??

again, do you know what is the quadrature mixer?

Oh, I just haven't noticed that you are talking about QUADRATURE mixer.

I know what a quadrature mixer is. If properly driven it has to reject one sideband.
So in your case, supposing you are rejecting the lower sideband, the output frequency have to be 4.02 GHz only.

See this example:

This doesn't appear appear from the time domain signal you plot. But there is no time scale, so I cannot understand what signal really is.

If you send a schematic with also the IF and LO input signals, I can try to help you, otherwise I'm not able to do it.

i am confused that what is the correct output wave of the quadrature mixer

and how to simulate the characteristic of the quadrature mixer like the conversion gain , IP3, and so on !


If you drive it properly (as you can see fro the previous attached plot), you have to see a sine wave at the output.
Be sure of:
-drive the linear port with a signal level below input compression point.
-drive le LO port with enough amplitude.

If you plot the signals in the freq domain you will be able to analyze better the steady state of the circuit.
I hop it can help.

and how to simulate the characteristic of the quadrature mixer like the conversion gain , IP3, and so on !


What you exactly need to know?

There are a lot of simulation techniques for the parameters of a mixer, depending on:

-the simulator you have
-if they are small signal or large signal
-and so on...

so, please be more detailed. -thanks.

cadence specRF

the IF range from the small signal to large signal,

and i want to simulation the characteristic of the quadrature mixer as much as possilble!


In spectreRF
PXF: to find correct indexes to work with.
Gain, noise figure: PSS (LO large signal) pac (as input signal), pnoise
P1dB: PSS (LO large signal, Input single tone Large signal), sweep input tone
IP3:pSS (LO large signal, Input double tones Large signal), sweep input tones.
I hope it can help.

pardon,can you give a example,

I am the first time to do the Rf circuit, sorry!

It would be too long to explain all simulator issues and properties. See in cadence user manual.

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